The present invention relates to a vehicular headlamp which provides low-beam illumination with a light distribution pattern having both a horizontal cutoff line and a diagonal cutoff line.
As is shown in FIG. 7, conventionally, as a low-beam light distribution pattern for a vehicular headlamp, a light distribution pattern P is often employed which has a horizontal cutoff line CL1 and a diagonal cutoff line CL2. In this low-beam light distribution pattern P, the horizontal cutoff line CL1 is disposed on the side closer to oncoming traffic, while the diagonal cutoff line CL2, which slopes upwards at an angle of about 15xc2x0 from the horizontal cutoff line CL1, is disposed on the same side as that on which the vehicle is traveling. The intention of this arrangement is to prevent the driver of an oncoming vehicle from being blinded by glare while maintaining good forward visibility for the driver of the vehicle.
In order to obtain this type of low-beam light distribution pattern, a light source 2 is disposed coaxially with the lamp unit reference axis Ax that extends in the longitudinal direction of the vehicle, and light from this light source 2 is reflected forward by a reflector 4.
However, when employing a light distribution pattern having a horizontal cutoff line CL1 and a diagonal cutoff line CL2 as the light distribution pattern P for the low beam, the long distance visibility may be insufficient for some drivers.
In view of the foregoing, it is an object of the present invention to provide a vehicular headlamp which performs low-beam illumination with a light distribution pattern having both a horizontal cutoff line and a diagonal cutoff line in such a manner as to improve the long distance visibility on the road on which the vehicle is traveling.
The present invention achieves the above object by forming a predetermined upward deflecting reflecting element on the reflecting surface of a reflector.
Namely, in accordance with the invention a vehicular headlamp is provided having a light source disposed substantially coaxial with a lamp unit axis that extends in the longitudinal direction of the vehicle and a reflector for reflecting light from the light source forward. The reflector is constructed to perform low-beam illumination in a light distribution pattern having a horizontal cutoff line and a diagonal cutoff line that slopes upwards at an angle of about 15xc2x0 from the horizontal cutoff line towards the road on which the vehicle is traveling. The vehicular headlamp of the invention is characterized in that an upward deflecting reflecting element for irradiating a beam towards a space in an area above the diagonal cutoff line is formed on an outer peripheral edge of the reflecting surface.
The above xe2x80x9clight sourcexe2x80x9d is not limited to any specific type so long as it is disposed substantially coaxial with the lamp unit reference axis. For example, the light source may be a filament such that of a halogen bulb, or the discharge light emission portion of a discharge bulb may be used.
The shape of the profile and the shape of the surface of the above xe2x80x9cupward deflecting reflecting elementxe2x80x9d is not particularly limited so long as it is formed to irradiate a beam onto the space around the area above the diagonal cutoff line.
The phrase xe2x80x9cto irradiate a beam onto the space around the area above the diagonal cutoff linexe2x80x9d not only refers to the case in which the beam is irradiated only to the space around the area above the diagonal cutoff line, but also to the case in which the beam is irradiated from the space around the area above the diagonal cutoff line to the space around the area above the horizontal cutoff line.
With the above-described structure, the vehicular headlamp according to the present invention provides low-beam illumination with a light distribution pattern having horizontal and diagonal cutoff lines. The upward deflecting reflecting element is formed at the outer peripheral edge portion of the reflecting surface of a reflector for irradiating the beam onto the space around the area above the diagonal cutoff line, thus providing the operational effects described below.
Generally the light distribution pattern formed by light reflected from the outer peripheral edge portion of the reflecting surface is small and and it exhibits a high luminous intensity. Therefore, if the upward deflecting reflecting element is formed at the outer peripheral edge portion of the reflecting surface, it is possible to irradiate a beam that forms a small light distribution pattern exhibiting high luminous intensity in the space around the area above the diagonal cutoff line.
As a result, according to the present invention, the long distance visibility on the road on which the vehicle is traveling can be improved for a vehicular headlamp structured to perform low-beam illumination in a light distribution pattern having a horizontal cutoff line and a vertical cutoff line.
Moreover, further in accordance with the present invention, the upward deflecting reflecting element is formed at the outer peripheral edge of the reflecting surface such that a light distribution pattern having a high luminous intensity can be formed. Accordingly, it is possible to obtain the desired beam for increasing the long distance visibility on the road on which the vehicle is traveling simply by constructing the upward deflecting reflecting element as an extremely small area.
In the above-discussed structure, the illumination angle and brightness of the beam that is irradiated onto the space in the area above the diagonal cutoff line are not limited so long as they allow the desired increase in long distance visibility on the road on which the vehicle is traveling. If, however, the beam illumination provides an luminance of 0.8 lux or more at a distance 25 meters to the front of the lamp unit in the direction about 0.5xc2x0 above the lamp unit reference axis and about 1xc2x0 towards the road on which the vehicle is traveling, the desired increase in the long distance visibility thereon is assured.
There is no particular limitation concerning the position at which the upward deflecting reflecting element is formed so long as it is on the outer peripheral edge portion of the reflecting surface. However, if the upward deflecting reflecting element is formed within an angle range of not more than about 30xc2x0 above the lamp unit reference axis, it is possible to obtain the beam needed to increase the long distance visibility on the road on which the vehicle is traveling with a small upward deflection angle. As a result, the long distance visibility on the road on which the vehicle is traveling can be increased without exerting an excessive burden on the shape of the reflecting surface. The upward deflecting reflecting element may be formed on either the left or right side of the lamp unit reference axis, or an upward deflecting reflecting element may be formed on both sides of the lamp unit reference axis.
If the upward deflecting reflecting element is constructed to deflect light from the light source for upward reflection by 1xc2x0 to 2xc2x0, the long distance visibility on the road on which the vehicle is traveling can be increased without requiring upward illumination over an unnecessarily wide range.
Provision of the upward deflecting reflecting element as described above makes it possible to improve the long distance visibility on the road on which the vehicle is traveling. However, the contrary situation may also be considered. That is, it may be preferred to give precedence to preventing any possibility of increasing the glare inflicted on pedestrians walking along the road, rather than to improving the long distance visibility.
In order to cope with such conflicting situations as described above, the lamp unit may be provided with a shade for shading light emitted from the light source onto the upward deflecting reflecting element. The shade may be selectively used depending upon the situation at hand, that is, either giving precedence to improving the long distance visibility or preventing the possibility of increasing the glare inflicted on pedestrians, while keeping the basic structure of the lamp unit common.
In the above case, for a lamp unit structure that gives precedence to improving the long distance visibility, the shade is no longer an essential structural element. However, the shade is effective for other purposes as well, for example, for the purpose of shading direct light irradiated from the light source to the front of the lamp unit. In cases such as this, partial modification of the shade structure may easily change the lamp unit structure to the one used to give precedence to prevent infliction of glare on pedestrians.